Lymphatic drainage of the trunk: Radiation induced no flow zone of mastectomy skin flaps-A cross-sectional study.

Changes in the lymphatic flow from the trunk following mastectomy, sentinel lymph node biopsy, axillary lymph node dissection, and radiotherapy remain understudied. We aimed to illustrate the altered lymphatic drainage pathways of the trunk following breast cancer treatment. We conducted a retrospective review of patients with breast cancer who underwent truncal lymphography between December 2014 and January 2024. Using a standardized imaging protocol, we recorded dermal backflow patterns, zones of absent lymphatic flow, and drainage pathways to the surrounding lymph node basins. Patients were grouped into radiated or non-radiated cohorts based on their treatment history and lymphatic drainage patterns from the chest wall were compared. Among the 173 hemi-trunks (95 patients), 73 (42%) received radiation therapy. Absence of lymphatic flow in the superior and inferior mastectomy flaps was observed in 66% of the cases. Multivariable regression analysis, accounting for radiation, mastectomy, axillary lymph node dissection, and chemotherapy, revealed that radiation was associated with a 142% increase in the odds of absent lymphatic flow to the inferior flap (OR 2.42, confidence interval, 1.05-5.55, p=0.038). Additionally, the radiation group demonstrated a significant increase in contralateral axillary lymph node drainage. This study highlights the impact of radiation therapy on the lymphatic anatomy of the trunk, inducing the no flow zone in mastectomy flaps. These findings are clinically significant for reconstructive surgeons, as lymphatic stasis in radiated flaps may compromise surgical outcomes. Lymphatic specialists can leverage this knowledge to optimize lymphatic drainage from the mastectomy flap using conservative and surgical approaches. LAY SUMMARY: Radiation therapy for breast cancer treatment significantly damages the lymphatic pathways in the chest. We showed that radiation increases the incidence of no lymphatic flow zones within mastectomy flaps. This knowledge can help improve the management of lymphatic drainage after cancer treatment.